The present invention relates to optical switch devices for use in optical communications systems. It finds particular application in conjunction with a heat sink for eliminating local heating in Microelectromechanical Systems (MEMS)-based optical switch devices, and will be described with particular reference thereto. It is to be appreciated, however, that the present invention is also applicable to other high speed optical switch devices, such as liquid crystal (LC)-based optical switches.
Optical communication systems are a substantial and rapidly growing part of communications networks. xe2x80x9cOptical communication system,xe2x80x9d as used herein, relates to any system that uses optical signals to convey information across an optical transmission device, such as a fiber-optic cable. Such optical communication systems include, but are not limited to, telecommunications systems, cable television systems, and local area networks (LANs).
As optical communication systems assume a greater role in communications networks, there exists a need for a cost-effective way to increase the capacity of existing optical transmission devices. While the overall capacity of optical communication systems may be expanded, e.g., by laying more fiber-optic cables, the cost of such expansion is somewhat prohibitive.
Dense Wavelength Division Multiplexer (DWDM) systems have been adopted as a means to increase the capacity of existing optical communication systems. DWDM systems enable information, in the form of multiple optical signals, to be delivered inside a fiber-optic cable at multiple wavelengths. The increase in bandwidth is limited only by the number of wavelengths that can be superimposed on a fiber. During transmission, information is packaged within phase modulated carriers at specific wavelengths and superimposed or multiplexed on the fiber. During reception, the carriers are separated or demultiplexed.
The ability to switch or route signals from one transmission device to another is an essential part of effective optical communication systems. High-speed optical switch devices, such as the LC-based Wavelength Selective Switch(trademark) and the Dynamic Spectral Equalizer(trademark), both developed by Corning Incorporated, facilitate selective interaction with wavelengths entering the devices in multiplexed packets of multiple wavelengths carried in a single laser beam. Current LC-based switch devices are used in optical communication systems capable of multiplexing and demultiplexing up to 40 channels.
In LC-based switch devices, wavelength selection results from changes in the polarization of the multiplexed laser signal passing through the liquid crystal medium. The polarizations of the incoming wavelengths are rotated depending upon the voltage applied to the outer plates or electrodes, which house the liquid crystal. Switching is accomplished by directing light with differentially rotated polarizations through polarization sensitive filters and beam splitters, thus allowing the incoming light to be selectively directed to the proper output ports.
One type of LC-based optical switch is known as a transmissive LC-based switch. As shown in FIG. 1, the transmissive LC-based switch 100 includes outer electrodes 102, 103, which generally are thin films of a transparent and electrically conductive coating, disposed on opposite sides of the liquid crystal medium 104. The outer electrodes allow the laser light 106 to pass through the liquid crystal medium 104 with minimum light absorption or reflection.
As shown in FIG. 2, by utilizing a transmissive electrode 202 on the front side of the liquid crystal 204 and a reflective electrode 203 on the back side, a reflective LC-based optical switch 200 is formed. The reflective LC-based optical switch 200 provides increased polarization control of incoming light by passing the light through the liquid crystal more than once.
Another high speed optical switch device takes form in an optical cross connect device, which utilizes Microelectromechanical system (MEMS) mirror arrays to redirect a beam of light traveling in free-space along a first direction to a second direction. Demultiplexed signals enter the crossconnect and individual incoming wavelengths can be redirected to different outgoing fibers.
Optical devices that depend upon the reflection of laser light, such as the LC-based and MEMS-based optical switch devices described above, may be compromised by the highly focussed laser light to which they are exposed. For example, in MEMS-based switch devices, localized heating due to laser light exposure often leads to warping or general deformation of the reflective surface, which negatively affects performance. Similarly, in LC-based switch devices, localized heating of the reflective surface occurs, which often leads to alteration of the optical properties of the LC in the local region and diminished performance.
The present invention contemplates a new and improved optical switching device, which overcomes the above-referenced problems and others.
In accordance with one aspect of the present invention, an optical switch device, which redirects at least a portion of a beam of light traveling along a first direction to a second direction, includes a base member and a reflective panel pivotally connected to the base member. The reflective panel includes a first substrate, a reflective layer disposed above the first substrate, and a heat sink layer disposed between the first substrate and the reflective layer.
In accordance with a more limited aspect of the present invention, the heat sink layer is comprised of hydrogenated amorphous carbon.
In accordance with a more limited aspect of the present invention, the heat sink layer is comprised of diamond-like carbon (DLC).
In accordance with a more limited aspect of the present invention, the heat sink layer is comprised of diamond.
In accordance with a more limited aspect of the present invention, the optical switch device includes an actuator connected to the base member and the reflective panel. The actuator is operative to move the reflective panel between a reflective state and a non-reflective state.
In accordance with a more limited aspect of the present invention, the reflective panel includes a liquid crystal layer disposed above the reflective layer, a transmissive electrode layer disposed above the liquid crystal layer, and a second substrate disposed above the transmissive electrode layer.
In accordance with another aspect of the present invention, an optical communication system includes a plurality of input fibers operative to emit light beams and a first microelectromechanical mirror positioned to receive light beams emitted by at least one of the input fibers. The first microelectromechanical mirror is adapted to selectively reflect light beams along a plurality of paths. The first microelectromechanical mirror includes a substrate, a heat sink layer covering the substrate, and a reflective layer covering the heat sink layer. A plurality of output fibers receive reflected light beams.
In accordance with a more limited aspect of the present invention, the heat sink layer is comprised of diamond-like carbon (DLC) having a thickness between 2.0 nm and 4000 nm.
In accordance with a more limited aspect of the present invention, the optical communication system further includes a second microelectromechanical mirror positioned to receive light beams reflected by the first microelectromechanical mirror. The second microelectromechanical mirror is adapted to reflect light beams along a path toward at least one of the output fibers.
In accordance with another aspect of the present invention, a reflective optical switch device includes at least one substrate layer and a reflective layer for reflecting laser beams incident upon a local area. In this device, a method of dissipating heat from the local area of the reflective surface includes providing a hydrogenated amorphous carbon layer between the reflective layer and the substrate.
In accordance with a more limited aspect of the present invention, the providing step includes chemical vapor depositing the DLC on the substrate in a thickness of between 2.0 nm and 4000 nm.
In accordance with another aspect of the present invention, a method of making a reflective optical switch includes providing a first substrate layer and providing a hydrogenated amorphous carbon heat sink layer over the first substrate layer. The method further includes providing a reflective layer over the heat sink layer, where the reflective layer is suitable to redirect light beams incident thereon.
In accordance with a more limited aspect of the present invention, the method further includes providing a liquid crystal (LC) layer over the reflective layer and providing a transmissive electrode layer over the LC layer. A second substrate is then provided over the transmissive electrode layer
One advantage of the present invention resides in reduced localized heating and deformation of the reflective surface.
Another advantage of the present invention resides in preventing the alteration of optical properties in the local region.
Another advantage of the present invention resides in reduced surface roughness for the reflective surface.
Yet another advantage of the present invention resides in uniform heat distribution over the entire reflective surface.
Still other benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the preferred embodiments.